1. Field of the Invention
The present invention relates to anchoring elements for structural building components, and, more particularly to a tie anchor for sandwich panels of reinforced concrete which are used as wall members of a building.
2. Description of the Prior Art
Sandwich panels of the type mentioned above consist generally of two panel layers of reinforced concrete which hold between them an insulating layer of light-weight material, such as mineral wool, foamed concrete, vermiculite, or styrofoam and the like.
The sandwich panel, normally serving as an outside wall member of a building, is supported and fixedly anchored to the building by one of its concrete panal layers, while the other, outer, concrete panel layer and the intermediate insulating layer are attached to the first panel layer so as to be carried by that layer. For this reason, the outer panel layer of the sandwich construction is frequently thinner and lighter than the inner panel layer.
In order to attach and support the outer panel layer on the inner panel layer, it is necessary to use one or several tie members of steel which traverse the intermediate panel layer and have extremities which are anchored in the two concrete layers. It is known, for example, to use for this purpose flat bands or strips of heavy sheet metal which are shaped to have an undulating, or zigzag outline. This tie anchor, accordingly, has top loops and bottom loops which extend into the inner and outer concrete panels, respectively, where reinforcing rods reach through holes in the loop portions. A tie anchor of this type is disclosed in the German Offenlegungsschrift (Publ. Application) No. 24 03 717. The one-piece tie anchor which is disclosed in this publication has a number of undulations which run horizontally between the two concrete panel layers. In order to provide the required supporting function, the metal strip has to be of a width which is approximately equal to, or larger, than the spacing between the top and bottom loops of the anchor.
The aforementioned Published Application also discloses, as an improvement over the one-piece tie anchor, an arrangement of two narrow undulated anchor members which are attached to each other on the loops which are embedded in the outer panel layer and whose opposite loops are spread apart vertically, where they are embedded in the supporting panel layer, thereby forming a V-shaped tie.
Since sandwich panels of the type under consideration undergo different degrees of thermal expansion on their inner and outer concrete layers, it is necessary to provide a limited displaceability of one panel relative to the other. This limited mobility is made possible by the undulations of the above-described tie anchor which, having substantially parallel connecting portions between their top and bottom loops, respond in the manner of parallel links, whereby the material of the intermediate insulating layer is locally compressed or displaced by the small lateral displacements of the tie anchor leg portions.
In a paper entitled "Vorfertigung in der Bautechnik", published in the journal "DIE BAUTECHNIK", Vol. 32, Issue No. 9, Sept. 1955, p. 319 (adapted from an article in "Journal of the American Concrete Institute", Vol. 1954, Issue No. 2, p. 149), is further disclosed an anchoring method for sandwich wall panels which suggests the arrangement of a plurality of shear-resistant, transversely rigid connecting members which likewise have a zigzag outline. The lateral rigidity of this arrangement is the result of alternatingly oppositely inclined leg poritons of the tie members which thereby act as tension and compression members, respectively, much like the bracing members of a truss.
The transverse rigidity of the sandwich panel tie members just described precludes their use for applications which, for reasons of thermal expansion or otherwise, require a limited transverse mobility of the supported panel layer relative to the supporting panel layer. The first-mentioned tie anchor, on the other hand, by providing such transverse mobility, fails to maintain a predetermined position of the supporting panel layer. Ideally, therefore, the outer concrete panel layer should be fixedly positioned relative to the supporting panel layer at one point only, that point being preferably the center of the panel area, while provision is made for minor relative displacements between the two concrete panel layers everywhere else on the panel.